Temperature responsive accelerator pump



April 11, 1967 J. H. WINKLEY ETAL. 3,313,531

TEMPERATURE RESPONSIVE ACCELERATOR PUMP Filed May 20, 1965 FISE.

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INVENTORS JERRY HWINKLEY BY RGBERT. SMITH ATTORNEY United States Patent O 3,313,531 TEMPERATURE RESFGNSIVE ACCELERATR PUR/11 Jerry H. Winldey, St. Louis, and Robert J. Smith, Florissant, Mo., assignors to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed May 29, 1965, Ser. No. 457,276 6 Claims. (Cl. 2451-34) This invention relates to carburetors for internal combustion engines. In one of its aspects the invention relates to a carburetor provided with an accelerating pump operable responsive to throttle movement to enrichen the fuel mixture during acceleration. In another of its aspects the invention relates to an accelerating pump for a carburetor, which pump is responsive to temperature of the fuel being pumped to vary the quantity of fuel pump in accordance with the temperature.

Internal combustion engines, particularly automotive engines, require that additional fuel be charged into the carburetor during acceleration. A cold engine requires more fuel from the accelerator pump because of inecient vaporization, condensation upon cold surfaces, and to some extent because of distribution problems within the carburetor and engine manifold. After the engine has warmed up less fuel is needed from the accelerator pump because vaporization is more complete and there is little or no condensation. For these reasons most carburetors are equipped with an accelerator pump that is a cornpromise between the larger capacity pump desirable for cold starts and the smaller capacity pump required under normal operating temperatures.

It is an object of the invention to provide an accelerator pump for a carburetor which is responsive to temperature changes whereby an optimum amount of fuel will be discharged by the pump at all times. It is another object of the invention to provide an accelerator pump that will vent vapors formed at high temperatures under the piston or diaphragm of the pump.

According to the invention bimetallic elements are incorporated into the plunger or moveable wall of an accelerator pump in such a manner as to close a bleed passage when the fuel is cold and to open the passage for bypassing fuel when the fuel is Warm and to provide means for venting vapors formed under the plunger or moveable wall when the fuel is warm.

The details of the invention, as well as other objects and advantages will be apparent from a reading of the following specification, claims, and the drawing in which:

FIGURE l is a carburetor embodying an accelerator pump of the invention.

FIGURE 2 is a detail, partly in section, of one form of piston for use in an accelerator pump.

FIGURE 3 illustrates the use of the invention in a diaphragm pump.

FIGURE 4 is an enlarged view showing the arrangement of the thermostatic elements in a plunger.

FIGURE 5 is a plan view of one of the thermostatic elements used in the invention.

FIGURE 6 is an enlarged View of another thermostatic element used in the invention.

FIGURE 7 shows a modication of the plunger of FIGURE 4.

FIGURE 8 is a plot of pump discharge volume versus temperature.

Referring to the drawing, and in particular to FIGURE l, there is shown generally at l a typical carburetor for an internal combustion engine. The carburetor is provided with a fuel chamber 3 which normally includes a float and needle valve assembly, as is customary in carburetors. The oat regulates the fuel level and admits by 3,313,531 Patented Apr. 11, 195,7

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way of the needle valve, additional fuel as required. The carburetor is provided with an air horn 5 in which is rotatably mounted a choke plate 7 on a shaft 9 and which choke is controlled by a thermostatic element 10 as is customary. The bore of the carburetor is indicated at 12. The bore has a restriction or venturi 14 and a stacked venturi cluster 16, I3 into which a main fuel nozzle 20 discharges fuel. Downstream of the main fuel nozzle there is rotatably mounted a throttle plate 22 on a shaft 24. An arm 26 on shaft 24 is adapted to move a rod or link 28, which in turn moves another arm 30. The arm 38 is fastened to a shaft 32 journaled into the body of the carburetor. An accelerating pump arm 34 is also mounted on shaft 32 for actuating the accelerator pump. Arm 34 is connected to the stem 36 of the accelerator pump by way of an S-link 38.

The pump plunger assembly is shown in detail in FIG- URE 2. Attached to stem 36 is a headed pin 40 the head of which lits loosely into a passage 42 in plunger stem 44. One or more drilled holes 46 intersect passage 42. The plunger is provided with a cup of leather or other suitable material 4S. Cup 43 is secured to the stem by retainers Sii, 52. Interposed between the retainer 52 and cup 4S is a garter spring 54. Above retainer 50 there is a plunger actuating spring 56 which abuts another retainer 5S. Retainer 52 may be press iitted to the stem 44 or it may be fastened by other means as by threads. Retainer 52 is also provided with a passageway 60. Secured to the underside of retainer 52 is the thermostatic valve of the invention. The thermostatic valve is secured in place by a retainer 62.

The thermostatic valve of the plunger assembly of FIG- URE 2 is illustrated in greater detail in FIGURE 4. As shown, the thermostatic valve comprises a pair of bimetallic discs 64, 65. Each of the bimetallic discs has been curved or dished slightly to create the arcuate cross-section shown. The thermal characteristics of the bimetallic disc are such that, when the disc is cold it will be arched in one direction but when the disc is heated it will snap through to become arched in the opposite direction. By a proper selection of disc size and curvature, the snap can be made to occur through a rather narrow range of temperatures. Moreover, by proper selection of the materials of construction and thickness of the two layers of metal used, the disc could be made to snap at any desired temperature within reasonable limits.

Disc 64' is provided with a central hole or aperture 66 and disc is provided with one or more holes or apertures 67. As shown, the disc 64 is above disc 65 and the upper disc has an aperture in the center thereof. The lower disc 65 has the aperture away from the center so that a curved portion of the lower disc covers the aperture of the upper disc. It is preferable to arrange the discs with the one having the central aperture on top. However, the apparatus will work satisfactorily with the relationship of the discs reversed. During assembly of the plunger, the disc 64 is iitted into a recess in retainer 52 followed by disc 65 and the two are held in place by a retainer 62. It is not necessary that Ithe discs 64 and 65 iit tightly into the recess at the periphery of the discs and in fact a very small clearance is desirable. On the other hand it is desirable that ythe discs be compressed one against the other slightly by the retainer 62. When this is done the upper disc will seal while cold against the top portion of the recess and uid will thus be prevented from passing through the assembly.

Control of the maximum amount of fluid that can pass through the bypass is possible in either of two ways. The passageway 6i) can be of such a diameter as to limit or meter the amount of fuel passed through it. In similar fashion passageway 60 if of large diameter can be used only to pass the fuel and the aperture in disc 64 can be reduced to serve as a fuel limiting or metering aperture.

FIGURE 3 illustrates the adaptation of the thermostatic valve to a diaphragm type pump. All elements of the assembly are identical to the plunger described earlier, excepting that plunger cup is replaced by a diaphragm of flexible material shown at 47. The diaphragm is held to the plunger -assembly as heretofore described and is retained at its outer periphery by a retainer 49.

FIGURE 7 shows a modification of the thermostatic valve structure of FIGURES 2 and 4. The valve of FIGURE 7 differs from that of FIGURE 4 in that a spacer 80 is inserted between the outer edges of discs 64 and 65. The spacer 8G will insure that the discs are separated as they begin to relax due to increase in temperature.

FIGURE 8 illustrates the fuel pumping characteristics of an accelerator pump provided with a bypass and a bimetallic valve element according to the invention. The volume discharged by the pump per stroke is plotted against temperature. Maximum volume of fuel is pumped when the fuel and the pump are cold. As the temperature of the fuel rises, the thermo-discs `tend to relax slightly and there is a portion of the fuel that -is bypassed through the valve and the passage 60 to the region above ythe pump. At approximately the mid-point of the curve, the two discs snap to the reverse position and there is a somewhat more abrupt drop in the pump. Following this, lan additional rise in temperature causes the discs to become slightly more arched in the reverse direction thus bypassing still more fuel.

In operation, fue-l is drawn into the pump chamber `by way of a passage 70 (see FIGURE l) which communicates with the float bowl of the carburetor. Upon depressing the accelerator pedal, the throttle shaft 24 is rotated counter-clockwise, causing arm 25 to raise lever 28 which7 by way of the linkages shown, forces stem 36 downward. If the movement is rapid the head of stem drops downwardly in passage 42 and spring 56 is compressed. Discharge of the pump, then, is by way of the expansion of spring S6. The fuel is discharged from the pump chamber by way of passage 7 8 which terminates in accelerator jet 79.

On cold start bimetallic valve will substantially close olf the passage 60 to prevent Ibypassing fuel to the top of the pump piston. This is desirable for cold starts because of the inefficient vapor-ization of fuel in the manifold and because of the tendency for the fuel to condense on the cold surfaces. However, as the engine warms up, vaporization becomes more eicient and there is a reduced ytendency for any condensation. As the temperature risesV the volume of fuel discharged by the pump gradually decreases until the metering action of the bypass limits the total amount of fuel that can be bypassed. The effect of `the bypassing of fuel is illustrated in FIG- URE 8.

It is understood of course that the temperature `at which the thermostatic valve opens to bypass the fuel can be varied to suit conditions and can be selected as desired. Normally it will be found desirable that the thermostatic disc snap to the reversed position at a temperature in the vicinity of 85 to 90 degrees Fahrenheit. It has been found that the fuel requirement on acceleration for a warm engine may -be only 60 to 40 percent or even less of the requirement for a cold engine. A fuel pump constructed according to the invention satisfies this requirement.

Where a diaphragm type fuel pump is used, the operation is substantially identical to that of the piston type pump. Accordingly in the Iappended claims, where the term movable wall is used, it is intended that this cover either the piston type pump or the diaphragm type pump.

Another advantage exhibited by the accelerator pump of the invention is that the pump is inherently capable of venting any vapors that may 'form under the piston or diaphragm. At elevated temperatures vapors frequently form in the pump cavity under the piston or diaphragm and when this happens it `will force fuel out of the cavity through the accelerator jet into the carburetor barrel. Prior art pumps have attempted to solve the problem, thus created by installing check valves or similar mechanisms in the pump plunger. The use of a check valve is no longer necessary since the valve of the invention will open the bypass Whenever vapors could be formed and any such vapors will then pass upwardly and zbe vented into the fuel bowl. Accordingly, the pump of the invention is capable not only of reducing the quantity of fuel pumped at elevated temperatures, -as is desirable, but also vents the undesirable vapors that are formed at the same elevated temperatures.

As has been discussed earlier, many of the prior art accelerator pumps have represented a compromise between optimum for cold operation and optimum for warm operation. One result of this compromise is that the pump stroke is sometimes shortened and/or that the diameter of the pump is considerably reduced. When such a pump is installed on a multi-stage carburetor, there is little or no capacity remaining at the time the secondary stage of the carburetor comes into operation. If no acceleration fuel is available at the time the secondary stage -becomes operative, a sag or bump may be experienced by the operator'when he brings the secondary stage of the carburetor into use. Because the carburetor of the invention can be equipped with a larger diameter plunger, and even with a longer stroke pump, it is possible, where desirable, to insure that fuel will be discharged at the time the secondary stage of a multi-stage carburetor comes into operation.

Because of the construction of a pump made according to the invention, it is possible to regulate the quantity of fuel bypassed within rather precise limits. Thus for any engine and carburetor combination that requires a relatively small quantity of fuel under warm operation, the bypass can be made relatively large. For a carburetor and engine combination that requires a greater amount of fuel at under warm temperature operation, the bypass will be correspondingly smaller. As mentioned heretofore, the control of the quantity of fuel bypassed can be effected either by proper sizing of the passage 60 in the lower retainer of the piston or by properly sizing the orifice or aperture 66 in the valve element 64.

We claim:

1. In a carburetor, a mixture conduit for supplying a mixture of fuel and air to an engine, a throttle valve in said conduit, a fuel bowl, a fuel system for supplying fuel from said bowl to said mixture conduit, an accelerating pump chamber, a reciprocable movable wall in said cylinder movable in one direction to discharge fuel from said cylinder into said mixture conduit, and movable in the other direction to draw fuel from said fuel bowl into said cylinder, a mechanical linkage interconnecting said throttle valve and said movable wall, said mechanical linkage being adapted t'o allow the movable wall to discharge fuel through a jet into said conduit when moved in one direction, and to draw fuel into said pump chamber when moved in the opposite direction, a fuel bypass passageway incorporated in said movable wall, and a thermostatic valve comprising an upper arcuate disc having a centrally disposed aperture and a lower arcuate disc having at least 'one aperture located away from the center of said disc, said valve being positioned to prevent passage o-f fuel to said passageway when said movable wall is cold and to permit passage of fuel to said passageway when said movable wall is warm.

2. A carburetor according to claim 1 wherein said movable wall is a piston.

3. A carburetor according to claim 1 wherein said movable wall is a diaphragm.

4. In a carburetor having a mixture conduit for supplying a mixture of fuel and air to an engine, a throttle valve in said conduit, a fuel bowl, a fuel system for supplying fuel from said bowl to said mixture cond-uit, an accelerating pump adapted to draw fuel from said bowl and to discharge fuel into said conduit, said accelerating pump being mechanically linked to the said throttle valve whereby when said throttle valve is opened for acceleration, the said accelerating pump will be actuated to discharge additional fuel into said conduit, a piston for said accelerating pump, a piston stem, a fuel bypass passage in the stem of said piston, said bypass passage being adapted to communicate the region above the said piston with the region below the said piston, a bimetallic valve secured to the bottom of said piston in such a manner as to prevent passage of fuel to the said bypass passage when the bimetallic valve is at a low temperature, and adapted to permit passage of -uel to the said bypass passage when said bimetaliic valve is warm, said bimetallic valve comprising a pair of bimetallic discs, and means permitting entry of fuel to the region below said thermostatic element.

5. A carburetor according to claim 4 wherein the said pair of discs comprise one disc having a central aperture and t-he other disc has an aperture located away from center, each disc being arcuate in cross-section and the said discs are secured to the said piston in such a manner that while cold the arcuate portions oppose one another and the central portion of the other said disc seals ott the aperture in the said one disc.

6. A piston for the accelerating pump of a carburetor comprising a hollow elongated stem, a shoulder on said stem, a cross passage intersecting the hollow portion of said stem, a washer abutting said shoulder, flexible sealing material for sealing said piston to the cavity within which it operates, said flexible sealing material being adjacent to said washer and beneath the same, a retainer beneath said flexible sealing material secured to said stem whereby said exible sealing material and said washer are also secured to said stem, a bypass passage in said retainer, a recess in the bottom of said retainer, a bimetallic closure member comprising a pair of bimetallic discs for preventing passage of fluid to said bypass passage Iwhen said bimetallic member is at a low temperature and for permitting passage of fluid to said bypass passage when said bimetallic member is at a higher temperature, said bimetallic closure member being positioned in said recess, and securing means `for securing the said birnetallic member in said recess.

References Cited by the Examiner UNITED STATES PATENTS 1,763,361 6/1930 Kirby 1261-34 1,881,996 10/1932 Bicknell 261-34 1,896,499 2/1933 Tice 2.61-34 2,877,996 3/1959 Kinney et al. 261-34 HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner. 

1. IN A CARBURETOR, A MIXTURE CONDUIT FOR SUPPLYING A MIXTURE OF FUEL AND AIR TO AN ENGINE, A THROTTLE VALVE IN SAID CONDUIT, A FUEL BOWL, A FUEL SYSTEM FOR SUPPLYING FUEL FROM SAID BOWL TO SAID MIXTURE CONDUIT, AN ACCELERATING PUMP CHAMBER, A RECIPROCABLE MOVABLE WALL IN SAID CYLINDER MOVABLE IN ONE DIRECTION TO DISCHARGE FUEL FROM SAID CYLINDER INTO SAID MIXTURE CONDUIT, AND MOVABLE IN THE OTHER DIRECTION TO DRAW FUEL FROM SAID FUEL BOWL INTO SAID CYLINDER, A MECHANICAL LINKAGE INTERCONNECTING SAID THROTTLE VALVE AND SAID MOVABLE WALL, SAID MECHANICAL LINKAGE BEING ADAPTED TO ALLOW THE MOVABLE WALL TO DISCHARGE FUEL THROUGH A JET INTO SAID CONDUIT WHEN MOVED IN ONE DIRECTION, AND TO DRAW FUEL INTO SAID PUMP CHAMBER WHEN MOVED IN THE OPPOSITE DIRECTION, A FUEL BYPASS PASSAGEWAY INCORPORATED IN SAID MOVABLE WALL, AND A THERMOSTATIC VALVE COMPRISING AN UPPER ARCUATE DISC HAVING A CENTRALLY DISPOSED APERTURE AND A LOWER ARCUATE DISC HAVING AT LEAST ONE APERTURE LOCATED AWAY FROM THE CENTER OF SAID DISC, SAID VALVE BEING POSITIONED TO PREVENT PASSAGE OF FUEL TO SAID PASSAGEWAY WHEN SAID MOVABLE WALL IS COLD AND TO PERMIT PASSAGE OF FUEL TO SAID PASSAGEWAY WHEN SAID MOVABLE WALL IS WARM. 